Flatworm Facts: WORMS that can live INSIDE YOU | Animal Fact Files

Summary

Flatworms, or platyhelminthes, are a diverse group with over 20,000 species, including tapeworms, flukes, and free-living forms. Most are parasitic, relying on host organisms to complete their life cycle. These creatures have bilateral symmetry, no skeleton, or circulatory system, but possess a nervous system with brain-like structures. Flatworms can regenerate and reproduce both sexually and asexually. They vary in size from microscopic to 50 feet long. Some, like tapeworms, manipulate their hosts to survive, while others are free-living predators. Despite their simplicity, flatworms demonstrate fascinating survival strategies and adaptability.

Takeaways

• 😀 Tapeworms are the most well-known type of flatworm, but there are over 20,000 species of flatworms in total.
• 😀 Flatworms belong to the group Platyhelminthes and are commonly split into four subgroups: Turbellaria, Cestoda, Trematoda, and Monogenea.
• 😀 Turbellaria are free-living flatworms, while most other flatworms are parasitic and rely on host organisms to survive.
• 😀 Approximately 80% of flatworm species are parasitic.
• 😀 Flatworms have bilateral symmetry, meaning if cut in half, both halves mirror each other, and they may be the oldest ancestors of bilaterally symmetrical animals.
• 😀 Flatworms lack a skeleton, circulatory system, or respiratory system but do have a nervous system, including a brain and eye-like receptors called ocelli.
• 😀 Flatworms can move in various ways, using muscles to move in wave-like patterns or tiny feet (cilia) to glide along slime trails, similar to snails.
• 😀 Flatworms are soft-bodied and lack shells, unlike snails, and are not segmented like other types of worms.
• 😀 They live in diverse environments, from terrestrial regions to aquatic habitats, and even Antarctica.
• 😀 Some species of flatworms can regenerate from parts of their body, and many possess both male and female reproductive organs, allowing for asexual reproduction in some species.
• 😀 Parasitic flatworms, like tapeworms, can manipulate their hosts to help complete their lifecycle, such as causing fish to swim to warmer waters to make them easier prey for birds.

Q & A

What are the four main subgroups of flatworms?

The four main subgroups of flatworms are Turbellaria, Cestoda, Trematoda, and Monogenea, although there is some debate on this classification.

What distinguishes free-living flatworms from parasitic ones?

Free-living flatworms, like those in the Turbellaria subgroup, can live independently without a host, while most other flatworms are parasitic and require a host to survive and complete their lifecycle.

Why are flatworms considered bilaterally symmetric?

Flatworms are bilaterally symmetric because if you cut a bilaterally symmetric organism in half, both pieces would mirror each other, a feature shared by all bilaterally symmetric animals, including humans.

What does bilateral symmetry mean in terms of body structure?

Bilateral symmetry means that an organism's body can be divided into two equal, mirror-image halves, with one side being the mirror reflection of the other.

What systems do flatworms lack compared to more complex animals?

Flatworms lack a skeleton, circulatory system, and respiratory system, but they do possess a nervous system, including a brain and eye-like receptors called ocelli.

How do flatworms move?

Flatworms can move using muscles in a wave-like pattern, or some species use tiny feet called cilia on their undersides to move along slime trails, similar to snails.

What is the size range of flatworms?

Flatworms typically measure less than an inch (2.54 cm) in length, but some species, like tapeworms, can grow up to 50 feet (15.24 meters) long.

How do flatworms feed and excrete waste?

Flatworms have a single opening in their body that serves both as a mouth for taking in food and as an anus for excreting waste after digestion.

What types of food do free-living and parasitic flatworms eat?

Free-living flatworms are carnivorous and eat organisms ranging from single-celled protozoans to larger animals like crabs and mollusks. Parasitic flatworms feed on their hosts in various ways, depending on the species.

How do flatworms reproduce?

Flatworms typically possess both male and female reproductive organs, allowing them to reproduce with or without a partner. Some species can regenerate from parts of their original body.

How do parasitic flatworms manipulate their hosts for survival?

Some parasitic flatworms, like certain tapeworms, manipulate their hosts to complete their life cycle. For example, they can alter the behavior of their host (like a fish) to make it more vulnerable to predation by the host's next intended predator (like a bird).